The present invention relates to a device for controlling and/or monitoring of external technical processes, in particular a device for use in connection with safety-related controls. The device has an input function, an output function and a processing function and can be connected to at least one higher-level unit for transfer of process-influencing and/or process-monitoring signals to actuators and/or sensors by way of a bus system.
A programmable controller that can operate alone with an input, an output and a processing function is known from European Patent EP 0 499 675 B1.
Field bus systems or peripheral bus systems that are on the market today can be used only in a limited way for time-critical safety applications because they have undetermined or unacceptably long response times. To date, known applications of the communication medium have the disadvantage that signals for the fast reactions required to ensure safety or security cannot be transferred at the required speed from the central unit over the bus to the decentralized peripheral stations. This is because the guaranteed response time over the bus exceeds the time required for fast reactions. In this process, the guaranteed response time over the bus includes at least the signal run times over the bus and the processing time required by the central unit. In turn, the central unit processing time is composed at least of evaluating the bus protocols, plus the time for evaluating the input signals and for calculating the output signals.